Removal of Pb (II) and Cu (II) from aqueous solutions by NaA zeolite coated magnetic nanoparticles and optimization of method using experimental design

Abstract

Magnetic nanozeolites were synthesized through a new method and their abilities were evaluated toward adsorption of Pb (II) and Cu (II) from aqueous solutions. A multivariate optimization method using central composite design (CCD) was designed to obtain the best conditions of the adsorption. NaA zeolite because of its high affinity for the investigated ions was selected and was coated onto magnetic nanoparticles. The morphology and characterization of the adsorbent were studied by different techniques such as SEM imaging, FT-IR spectrometry and AGFM measurements. The most favorable conditions for Pb (II) removal was achieved in pH = 5.6 and 8 mg sorbent in a 750 mg L−1 Pb (II) aqueous solution when removal process was done in 8 min. Maximum removal of Cu (II) was attained under the optimal conditions with pH = 2.9, adsorbent amounts 16 mg, initial ion concentration 22.1 mg L−1 and sonication time 24 min. The predicted model of Design Expert software was indicated the significant main factors and the possible interactions of the factors. Based on the results, some interactions between the effecting factors were found for Pb (II) and Cu (II) ions and R2 was attained 0.99 and 0.97 for these ions respectively. Our findings clearly showed that magnetic nanozeolites can be made successfully by entering silica-coated magnetic nanoparticles into the initial solution of zeolite synthesis. Also, the coating of the magnetic nanoparticles with zeolite NaA improved effectively the adsorption of the selected ions while we can conveniently separate the nanozeolites with an external magnet.